It is known to examine and measure the extent of the deformation of an object with the aid of holography. Double exposure of hologram plates enables changes in shape to be made visible on a hologram, in the form of images having a larger or smaller number of stripes in different configurations. This enables extremely small changes in shape, e.g. deformations as small as 0.3 micron, to be measured, which is highly significant when monitoring the quality of or load testing mechanical constructions. In view of the very small dimensions concerned in this regard, it is important that shaking between objects being examined and hologram plates used to take the two exposures be prevented to the maximum extent possible. Previously, certain difficulties have been experienced in fulfilling these conditions without the use of excessively complicated and expensive arrangements.
An object of the present invention is to provide means which will enable two objects, e.g. industrial products and hologram plates, to be mounted in a manner which will substantially prevent shaking from occurring and which will enable the same relative positions between the objects to be re-established subsequent to having moved one of said objects.